The exchange and maintenance of genetic information in Escherichia coli will be studied employing biochemical and genetic techniques. Specifically experimentation will focus on four aspects of this problem. 1. The analysis of the role of the recB and recC gene products (exonuclease V) in DNA repair, cell viability and genetic recombination using a series of temperature sensitive mutants and recombinant plasmids which carry the recB and recC gene products. 2. Determination of the in vivo function of exonuclease I (xonA, sbcB) in DNA repair and genetic recombination through the use of hybrid lambda clones carrying both the wild type and mutationally altered gene. In addition, the cooperative interactions between exonuclease I, exonuclease V and DNA polymerase I will be examined in vitro. 3. The recF gene will be cloned and its product identified and purified. Attempts will be made to determine its role in DNA repair and genetic recombination. 4. The uvrD gene product will be purified and characterized employing a recombinant plasmid carrying the structural gene and an in vitro nick translation assay. An additional series of experiments will be undertaken to determine if eukaryotic nucleic acid enzymes can be functionally expressed in E. coli. These experiments are designed to determine if recombinant DNA techniques can be of use in the analysis of DNA repair and genetic recombination in Neurospora crassa and Saccaromyces cervisiae.